Comparative soil study in a mediterranean ecosystem ofQuercus pyrenaica(Willd.)

Abstract

A comparison was made of certain elements of the biogeochemical cycle of soils in forest ecosystems of the deciduous species Quercus pyrenaica (Willd.). Four sampling sites were selected in a rainfall gradient, with slight differences in the understory composition. Two of the sites were over schist and the other two over granites; however, the soil type (xerumbrepts) was similar for the four sites. Soil chemical and physicochemical parameters such as carbon, nitrogen, pH, cation exchange capacity (CEC), and exchangeable cations were monitored in the upper soil horizon (0–10 cm). Samples were collected every 3 months for 3 years. The final sample size was n = 96. An inverse relationship between rainfall and exchangeable cation concentration was found, with significant differences (p < .05) among the sites, with the exception of exchangeable sodium. The sum of cation values were 8.15 cmol kg^‐1 for site 1 (720 mm mean annual precipitation), 3.07 cmol kg^‐1 for site 2 (872 mm mean annual precipitation), 2.02 cmol kg^‐1 for site 3 (1245 mm mean annual precipitation), and 1.96 cmol kg^‐1 for site 4 (1580 mm mean annual precipitation). On the other hand, soil carbon, nitrogen, and CEC showed a less clear relationship to the precipitation. Lit‐terfall and aboveground characteristics were more decisive than rainfall in determining their values.